A 'preview diff' option when editing playbooks

[timlnx]

Would be nice...

https://docs.python.org/2/library/difflib.html#differ-example

1. You edit a playbook
2. You are prompted Upload? [Y/n] ('d' for diff)?:
3. If d then the diff is calculated with difflib.Differ and displayed in a pager
4. You quit the pager and are given the options:

• Upload
• Edit
• Pass